package com.open.common.persistence.dialect.db;

import com.open.common.persistence.dialect.Dialect;

/**
 * Dialect for HSQLDB
 */
public class HSQLDialect implements Dialect {
	@Override
	public boolean supportsLimit() {
		return true;
	}

	@Override
	public String getLimitString(String sql, int offset, int limit) {
		return getLimitString(sql, offset, Integer.toString(offset), Integer.toString(limit));
	}

	/**
	 * 将sql变成分页sql语句,提供将offset及limit使用占位符号(placeholder)替换.
	 * 
	 * <pre>
	 * 如mysql
	 * dialect.getLimitString("select * from user", 12, ":offset",0,":limit") 将返回
	 * select * from user limit :offset,:limit
	 * </pre>
	 *
	 * @param sql 实际SQL语句
	 * @param offset 分页开始纪录条数
	 * @param offsetPlaceholder 分页开始纪录条数－占位符号
	 * @param limitPlaceholder 分页纪录条数占位符号
	 * @return 包含占位符的分页sql
	 */
	public String getLimitString(String sql, int offset, String offsetPlaceholder, String limitPlaceholder) {
		boolean hasOffset = offset > 0;
		return new StringBuffer(sql.length() + 10).append(sql).insert(sql.toLowerCase().indexOf("select") + 6, hasOffset ? " limit " + offsetPlaceholder + " " + limitPlaceholder : " top " + limitPlaceholder).toString();
	}

}
